Funds are requested for a state-of-the-art macromolecular crystallography data collection instrument. We are specifically interested in purchasing an integrated system with a Rigaku RU- H3RHB X-ray generator, a confocal optical system (blue configuration), an inverse phi axis, an MSC R-Axis IV++ area detector, an X-stream cryogenic system, and a control computer with software to drive the instrument and process diffraction data. This new system will directly and immediately impact NIH funded projects among 8 research groups by ensuring adequate X-ray beamtime for crystal screening/characterization and complete data collections. It will complement our 9 year old R-Axis II system during downtime that is increasingly required for maintenance and repairs of this older model, and accommodate our growing need for the instrument. The expanded capabilities in macromolecular crystallographic data collection are vital to pursue the following projects: a) autoproteolysis through N -> O acyl shift, b) N-terminal nucleophile hydrolase, c) MspI as a new structural class of restriction enzymes, d) annexin crystal structures and membrane interactions, e) metal dependent complexes in blood coagulation, f) efflux-mediated resistance to tetracyclines, g) novel antioxidant mechanisms of surfactant proteins, h) structural and mechanistic studies of phosphonatase, i) deciphering the cellular functions of aldolase, j) enzymes in the meta-fission pathway, k) photoprotein aequorin, 1) multiple antibiotic resistance repressor MarR, m) nucleosome assembly chaperones, n) the apoptosome and its role in programmed cell death, o) lipoprotein structure and apoprotein conformation, p) ganglioside GM1-cholera toxin, q) LDL receptor-LDL complex, r) insulin receptor-insulin complex, s) human apolipoprotein C-1. Overall, these projects will apply macromolecular crystallography to enhance our understanding of the function and assembly of biomolecular complexes and cellular machines. These macromolecular assemblies play important roles in enzymology, signalling through membranes, and chromatin assembly. Furthermore, these studies will provide insights into glycoprotein function as well as cellular processes of lipid metabolism mediated by LDL and the formation of both normal and aberrant structures with medical relevance to atherosclerosis and AGU genetic disease.